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As the UK emerges from several weeks of cold weather, spare a thought for two Aberystwyth University glaciologists, who have just returned from fieldwork on the Antarctic Peninsula. Professor Michael Hambrey and Dr Bethan Davies had to man-haul all their equipment across the ice shelf to their base camp, a gruelling process of relaying that took three days in total. Once there, they camped in a rugged 3-person polar pyramid tent, cooking on a primus stove. It was extremely cold and there was no running water – snow had to be cut into blocks and melted for drinking and cooking.

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The Antarctic Peninsula Ice Sheet is interesting to glaciologists because it is responding rapidly to changes in ocean circulation and warming atmospheric temperatures. This warming has already caused the dramatic collapse of several floating ice shelves around the Antarctic Peninsula, such as the Larsen B Ice Shelf in 2002. Collapsing ice shelves are a particular concern, as they hold back the glaciers on the mainland. If the ice shelf in front of a glacier is removed, the glacier speeds up and becomes thinner, releasing more ice into the ocean and causing the sea level to rise. Scientists therefore want to know which ice shelves will collapse in the future, and how much impact this will have on future sea level rise.

The glaciologists spent five weeks in a remote field camp on Alexander Island, to the west of the Antarctic Peninsula. It is the second largest uninhabited island on Earth, covering an area nearly three times the size of Wales. The fieldwork complemented earlier satellite mapping of the ice shelf by two other Aberystwyth University glaciologists, Professor Neil Glasser and Dr Tom Holt.

The team were able to reconstruct the past behaviour of the floating ice shelf. The ice shelf has moved granite boulders from the Antarctic Peninsula onto Alexander Island, and they now rest at elevations of up to 140 m above the current ice levels. These “erratic” boulders (boulders that are not part of the local geology and have been glacially transported) document the past height and behaviour of the ice shelf. These boulders are now on ice-shelf moraines, and the range in heights of the ice-shelf moraines documents glacial unloading and the uplift of the land following deglaciation around 10,000 years ago. Understanding past glacial loading and rates of uplift allows scientists to calculate past ice volumes.

Understanding how the ice shelf behaved in the past should help scientists to understand how it will respond to changing climatic and oceanic conditions in the future. This is important, because if it melted, the Antarctic Peninsula Ice Sheet could raise global sea levels by up to half a metre. Combined with melting from mountain glaciers and the Greenland Ice Sheet, this could result in flooding of low-lying areas of Earth over the next century.

To try and understand the past behaviour of George VI Ice Shelf, the team mapped and collected samples from the surfaces of these erratic boulders. A technique called “cosmogenic nuclide isotope dating” is used to discover the length of time that the boulders have been exposed on the surface of the earth since their deposition by the ice shelf or glacier..

Dr Bethan Davies explained, “Cosmogenic nuclide isotope dating works because new isotopes are formed when the quartz in the rocks is hit by cosmic rays, which originate from outer space. By calculating the amount of cosmogenic isotopes in the rock, we can work out how long the boulder has been on the Earth’s surface”.

She added, “Because the geology of Alexander Island is so different to the rest of the Antarctic Peninsula, it is very clear where these boulders have come from, and that they have crossed George VI Sound. This helps us to reconstruct past ice-shelf behaviour”.

She went on to say, “This is a new technique but it is exciting because it will help us to answer important questions about past rates and magnitudes of change in ice shelves and glaciers. This will help us to better predict future ice sheet behaviour in this sensitive region.”

Professor Michael Hambrey commented: “Our field area was chosen because it is one of the largest ice-free areas in the Peninsula, and it records changes in both the ice sheet and local mountain glaciers. Most previous work has been undertaken offshore from large research vessels. Our work therefore fills an important gap in our knowledge.”

He added: “We were privileged to work in a stunningly beautiful area. The vast George VI Ice Shelf, with innumerable ice-draped mountains poking through the Antarctic Peninsula Ice Sheet in the far distance, conveys an image of permanence. Yet we know that warming is having the insidious effect of eating away the ice shelf. The nearby Wordie Ice Shelf has already collapsed, so we have to assume this ice shelf is also vulnerable”.

The research was funded by the UK Natural Environment Research Council (NERC) and supported by the British Antarctic Survey (BAS), who organised the fieldwork on Alexander Island. BAS supplied all the fieldwork logistics including transport, the field camp and safety equipment, together with an accompanying staff member – Ian Hey, a field assistant and mountaineer. The project is led by Professor Neil Glasser from Aberystwyth University, and is part of a larger NERC-funded project that aims to reconstruct glacier change across the Antarctic Peninsula over centennial to millennial timescales

CONTACT DETAILS:

Bethan Davies: bdd@aber.ac.uk

Michael Hambrey: mjh@aber.ac.uk

LINKS:

Blog and more photographs by Bethan Davies: www.AntarcticGlaciers.org